The IP Multimedia Subsystem (IMS) is a standard defined by the 3rd Generation Partnership Project (3GPP) for the next-generation network, and its distinguishing features are that the Session Initiation Protocol (SIP) system is adopted, communication is unrelated to access, and multiple capabilities, such as separation between a multimedia service control function and a bearing capacity, separation between a call and a session, separation between an application and a service, separation between a service and a network, and service convergence of a mobile network and Internet, can be provided.
The presentation of IMS complies with the trend of integrative development of a communication network; a network architecture of the IMS is shown in FIG. 1, including: a piece of User Equipment (UE)/access equipment, a Proxy Call Session Control Function (P-CSCF), an Interrogating Call Session Control Function (I-CSCF), a Serving Call Session Control Function (S-CSCF), a Home User Server (HSS) and an Application Server (AS) which is not shown in FIG. 1.
A Public User Identity (PUI) is an identity for a user to communicate in the IMS network. For meeting requirements of some service applications in specific scenarios, a concept of alias group is introduced into the IMS, wherein the alias group is information about which specific numbers of a user are aliases to each other, for example, PUI 1 and PUI 2 are aliases to each other, namely PUI 1 and PUI 2 represent the same user.
A Uniform Resource Identifier (URI) in the same alias group has the following features: belonging to the same implicit registration assembly, subscribing the same service, and having completely same configuration in each service scenario.
In an IMS architecture, an S-CSCF can acquire alias group information by acquiring user data information from an HSS; the specific flow is shown in FIG. 2, including the following steps:
S201: UE sends a registration request to an P-CSCF, wherein the registration request carries a PUI;
S202: when receiving the registration request, the P-CSCF locates local user data; the P-CSCF finds an I-CSCF through a Domain Name System (DNS) or other ways, and forwards the registration request to the I-CSCF;
S203: the I-CSCF sends an S-CSCF assignment request (UAR) to the HSS to require assigning the S-CSCF;
S204: the HSS returns an S-CSCF assignment answer (UAA) to the I-CSCF, wherein the S-CSCF assignment answer includes an S-CSCF address/name assigned to the user, and user data including alias group information of the user;
S205: the I-CSCF sends a registration request message to the selected S-CSCF;
S206: the S-CSCF sends a user data acquisition request (SAR) to the HSS to acquire the user data;
S207: the HSS returns a user data acquisition answer (SAA) carrying the user data, wherein the user data includes the alias group information of the user;
S208: the S-CSCF processes correspondingly, and returns a registration success response, like 200OK, to the I-CSCF, wherein the response includes PUI information; at the same time, the alias group information of the user is stored locally;
S209: the I-CSCF forwards the registration success response to the P-CSCF;
S210: after receiving a registration response message, the P-CSCF stores the user data locally, that is, storing the PUI information locally; and
S211: the P-CSCF forwards the registration success response to the UE.
Through the alias group technology, the S-CSCF can associate different numbers. For example, PUI 1 and PUI 2 are associated numbers to each other, wherein PUI 1 is sip: +861013813812345@bj.com.cn; PUI 2 is tel: +861013813812345. For some functions, it is required to use associated numbers. By taking a monitor function for example, it is supposed the PUI 1 is monitored, then, since PUI 1 and PUI 2 have the same number service and the same nature, it is necessary to monitor PUI 1 and PUI 2 simultaneously for preventing missing monitoring. For the S-CSCF, the alias group technology can solve the number association problem and realize simultaneous monitoring of PUI 1 and PUI 2.
At present, the P-CSCF has neither number association information nor alias group information. When some functions, such as a monitoring function, are implemented on the P-CSCF, it is needed to monitor all number forms of a user in order to efficiently prevent missing, which is complicated to operate and costs too much.